Method and apparatus for judging the conditions of blast furnace

ABSTRACT

AMONG THE SOLID BORNE SOUNDS GENERATED BY THE MANTLE OF THE BLAST FURNACE IN OPERATION, THE MAGNITUDE OF THE LEVEL OF THE SOLID BORNE SOUNDS WITHIN THE SPECIFIC FREQUENCY BAND IS CORRELATED WITH THE CONDITIONS OF THE BLAST FURNACE, FOR EXAMPLE, SLIPPIN, HANGING OR FALLING OF THE HANGING. A DETECTOR DETECTS SOLID BORNE SOUNDS FROM THE MANTLE   OF THE BLAST FURNACE, A BAND PASS FILTER CIRCUIT SELECTS THE SOLID BORNE SOUNDS WITHIN THE SPECIFIC FREQUENCY BAND, AND AN INTEGRATION CIRCUIT PRODUCES SIGNALS EXPRESSING THE MEAN INTENSITY LEVEL OF THE SELECTED SOLID BORNE SOUNDS. THROUGH THE SIGNALS THE CONDITION OF THE BLAST FURNACE IS JUDGED.

Nov. 14, 1972 NAOTERU ODA ET AL 3,702,694

METHOD AND APPARATUS FOR JUDGING THE CONDITIONS OF BLAST FURNACE FiledMay 12, 1971 B Sheets-Sheet 1 I STOCK LINE 5TH DECK 4TH DECK 3RD DECKTHE MEASUR- ING POINTS OPTIMUM 2ND DECK 1ST DECK HEIGHT OF SHAFTiNvENToRs. No: ohru 00 Sa'l'ctu r' N s n u r4 MJz 0 Kowafs n Q5, Mm 4A0!M A-aer5 Nov. 14, 1972 NAOTERU ODA ET AL 3,702,694

METHOD AND APPARATUS FOR JUDGING THE CONDITIONS OF BLAST FURNACE FiledMay 12, 1971 8 Sheets-Sheet 2 5 0 4TH DECK B o 3RD DECK o 2ND DECK w 5 8o g .0 8 w 0 2| O 8 n m 0.6 0.7 0.8 Q9 L0 L2 L4 TOTAL THICKNESS (I WALL(m) 3 WM awn AcgNfS Nov. 14, 1972 NAOTERU ODA ETAL 3,702,694

METHOD AND APPARATUS FOR JUDGING THE CONDITIONS OF BLAST FURNACE FiledMay 12, 1971 8 Sheets-Sheet 4.

NORTH d 20- a M 1 O L FIG. 3C 20 EAST o O- m L SOUTH 9 L 20 WEST U) 0 AW T|ME (Hr) FIG. 30

50mm BORNE souwo LEVEL 7* -TIME (day) INVENTOR fiqo'fli'u OJQ su' l 1'.M'shimur Ilia/10 kbma'l'su Nov. 14, 1972 NAOTERU ODA ETAL 3,702,694

METHOD AND APPARATUS FOR JUDGING THE CONDITIONS OF BLAST FURNACE FiledBay 12, 1971 6 Sheets-Sheet 6 F/g. 3E

\NVENTORS. A/aa1crm OJQ 1; M'shi ra Ih'aho Komanad 3 We! Md Acewr;

Nov. 14, 1972 NAOTERU ODA ETAL 3,702,694

METHOD AND APPARATUS FOR JUDGING THE CONDITIONS OF BLAST FURNACE FiledMay 12, 1971 8 Sheets-Sheet 6 ,0 3RD DECK,NORTH J 3RD DECK. EAST LU IO-l O O -|0 3RD DECK,SOUTH E ZOWC O an O 3 o O 3RD DECK, WEST HANGING VERYW BAD e000 2v, WM M Ana-N AGENTS Nov. 14, 1972 NAOTERU ODA ETAL3,702,694

METHOD AND APPARATUS FOR JUDGING THE CQRDITIQNS OF BLAST FURNACE FiledMay 12, 1971 8 Sheets-Sheet 7 4TH U'ICK, NQRTH IO- M A m 4TH DECK.EASTuJ IO- 0 Z 5 --IO M 4TH IECK. SOUTH E M O [D o.

4TH DECK. WEST 20- lO-W HANGING- VERYBAD- BAD GOOD l 1 --TlME(Hr)INVENTOR5: Naofcru Ody, Scfiehi Nr shlmurq Hie/co Komafsu AGENT;

Nov. 14, 1972 NAOTERU 00 ET AL 3,702,694

METHOD AND APPARATUS FOR JUDGING THE CONDITIONS OF BLAST FURNACE FiledMay 12. 1971 8 Sheets-Sheet a |NVENTOR55 Nag hr-h Od S il'zhf N JII M umH e co Kama H mam Md 8 1 mwh United States Patent 3,702,694 METHOD ANDAPPARATUS FOR JUDGING THE CONDITIONS OF BLASI FURNACE Naoteru Oda, Kobe,Seiichi Nishimura, Takatsuki, and I-Iideo Komatsu, Suita, Japan,assignors to Sumitomo Metal Industries, Ltd., Osaka, Japan Filed May 12,1971, Ser. No. 142,605 Claims priority, application Japan, May 20, 1970,45/ 43,510 Int. Cl. C21b 7/24 US. Cl. 266-27 6 Claims ABSTRACT OF THEDISCLOSURE Among the solid borne sounds generated by the mantle of theblast furnace in operation, the magnitude of the level of the solidborne sounds within a specific frequency band is correlated with theconditions of the blast furnace, for example, slipping, hanging orfalling of the hanging. A detector detects solid borne sounds from themantle of the blast furnace, at band pass filter circuit selects thesolid borne sounds within the specific frequency band, and anintegration circuit produces signals expressing the mean intensity levelof the selected solid borne sounds. Through the signals the condition ofthe blast furnace is judged.

The present invention relates to the method and apparatus for judgingthe conditions of the blast furnace by detecting the solid borne soundsgenerated in the mantle of the furnace during operation.

It has always been desirable to examine directly the conditions in theinside of the blast furnace during op eration. This has not beenaccomplished owing to the high temperature and to the vastness of thecapacity of the furnace, with the only exception being that a soundingrod is used for judging the conditions of the furnace indirectly andintermittently. In this conventional method, a rod is lowered from thetop of the furnace until it reaches the top of the burden (chargedmaterials), then the reading of the rod, expressing the fall of thestock level within the furnace, is visually observed or recorded byremote control to thereby estimate the conditions of the furnaceintermittently. Although the conventional method is effective inestimation of the overall hanging wherein the level fall of the burdencompletely stops, it has such disadvantages that it is not alwayseffective in estimation of the creation and the growing stage of localhangings, which is particularly important in operation, and that thesounding rod must be drawn up each time when ores and coke are chargedand again lowered after the ores and coke are charged.

The conditions of the furnace can be estimated to some extent only byfluctuations of the discharge and the hot air pressure. However, themeasured values of these factors are related to the resistance of theentire blast furnace. Therefore, it is difiicult to detect the growth ofthe local hangings by the measurement of such factors.

The solid borne sounds of the mantle of the blast furnace are producedby mixed propagation of sounds generated by the burdens being disturbedwithin the furnace and the gases passing through the burdens. And it hasbeen found that a specific solid borne sound contains variousinformation through which change of the condition within the furnace canbe estimated. In other words, it has been found that the condition ofthe blast furnace can be detected by extracting the fluctuation ofintensity level of selected solid borne sounds.

A feature of the present invention is that the condition of the blastfurnace which is constantly changing with the progress of the furnaceoperation can be estimated continuously by the changes of reading of themeasurement charts.

Another feature of the present invention is that the transition of blastfurnace condition can be foreseen by detecting the signals following thechanges of the furnace conditions in the neighborhood of the measuringpoints of the furnace.

Taking advantage of the fact that a component of relatively highfrequency among solid borne sounds of the blast furnace mantlefaithfully follows the sounds corresponding to the furnace conditions inthe neighborhood of the measuring points, the present invention intendsto control the furnace with stability and to thereby facilitateproduction increase and normal operation by providing a plurality ofsolid borne sound measuring devices around each deck of the furnace,detecting the changes of furnace conditions nearby the measuring points,foreseeing the transitions of the furnace conditions such as hanging,slip, local change of the wall thickness, analyzing them and takingnecessary correcting control.

An object of the present invention is to detect changes of conditions atthe points within the furnace, to foresee the transition of the entirefurnace condition, and to thereby promote the normal operation of thefurnace. In the apparatus according to the present invention, aplurality of solid borne sound detectors are mounted at a plurality ofspecific points on the blast furnace mantle for detecting changes of thefurnace wall thickness, changes of the burden and the positions thereofthrough the magnitude of the level of the sounds in the specificfrequency band within an octave above and below 8,000 Hz. at eachmeasuring point and the furnace is controlled through the signals.

In the present invention, a specific frequency band, an octave rangefrom 5,600 Hz. to 11,200 Hz., is selected firstly because the frequencyof the sound generated by the hot air blasted into the furnace andpassing through the charged materials is around 8,000 Hz. and this ispresumed to be the frequency representing the reactions within thefurnace, and secondly because the frequency band around 8,000 Hz. is farfrom the 1,000 Hz. band representing the combustion sounds nearby thetuyere and various mechanical operation sounds and thereforesubstantially free from noises disturbing the judgment of the conditionof the blast furnace.

FIG. 1 is a schematic illustration of the optimum points on the blastfurnace mantle for detecting the solid borne sounds, the mantle beingshown in elevation and partly in section;

FIG. 2 is a graphical illustration of the correlation between the totalthickness of the furnace wall including the deposits and the solid bornesound level;

FIGS. 3(A)-(E) are oscillograms showing changes of the solid borne soundwith time in various conditions of the furnace;

FIGS. 4(A) and (B) are graphical illustrations of the correspondingrelationship between the solid borne sound level and the condition ofthe furnace shown in contrast to each other in comparatively long time;and

FIG. 5 is a block diagram of the apparatus according to the presentinvention.

An embodiment of the present invention will be explained in detail withreference to the accompanying drawings.

FIG. 1 shows positions on the mantle where the solid borne sounddetectors are to be mounted. The detector is a piezo-electric typepick-up made of, for example, barium or zirconium titanate. It ispreferable that four detectors are provided at each height of 2ndthrough 4th decks around the furnace, one at every in other words, one

each at north, east, south and west of each height around the furnace of2nd through 4th decks. It should be noted that the detectors will catchnoise signals at higher positions, namely close to the stock level ofthe furnace and at lower positions, namely close to the belly, causedrespectively by charging sounds at the top and combusting sounds nearthe tuyere. The preferable mounting positions of said pick-ups(detectors) are referred to in FIG. 1 as 2nd through 4th decks above.However, since such expression may not give the same definitions of thepositions in a furnace of different capacity, type or construction, theoptimum detecting positions are shown in Table l with reference to theshaft height (from the belly to the stock line).

TABLE 1 Optimum detecting positions Shaft Height from Capacity height,In. the belly,rn. Shaft ratio A 14.3 s-11.9 1. s/4-3. an 15.3 5-ll. 5 1.3l-l-314 20. 8 5-12.6 1/4-2.4/

Therefore, the range of the optimum detecting points is from A to A ofthe height of the furnace, and it is preferable that the lowest limit beset at least 5 meters higher than the belly.

In FIG. 2, the relationship between the solid borne sound level (db),obtained by amplifying the sound signal detected by said solid bornesound detector, passing the amplified sound signal through a band passfilter from 5,600 Hz. to 11,200 Hz. and logarithmically compressing, andthe thickness of wall (meter) at each detecting point is plotted. Thereis a strong positive correlation and rectilinear relation between theabsolute values of the solid borne sound level and the total thicknessof the Wall including the deposits as shown in FIG. 2. After thecorrelation between the total wall thickness and the average solid bornesound level is obtained, further variation of the wall thickness can beestimated through it with an accuracy of at least :75 mm.

FIG. 3 shows oscillograms expressing the solid borne sound levelsmeasured at the 4 points: north, east, sound and west around the furnacemantle at the height of the 3rd deck (at the middle of the shaft height,see FIG. 1) under various furnace conditions. FIG. 3(A) shows thecondition of normal operation, wherein no noticeable variation is seenat each level and the magnitude at each level directly corresponds tothe thickness of the entire furnace wall including the deposits nearbyeach detecting point. In such a condition, the absolute value of theentire wall thickness can be obtained directly from FIG. 2. The furnacewall is thick in the east to west direction and thin in the north tosouth direction.

FIG. 3(B) is an oscillogram of the solid borne sound level in thecondition that the ball of the burdens within the furnace becomessomewhat discontinuous and the fall is not proceeding uniformly at eachloctaion. This phenomenon occurs almost always immediately after thecharging. It is very important as a source of information for normaloperation of the blast furnace to be able to understand the so-calledhabit, namely the tendency that the fall of the burdens does notprorceed uniformly at the north, east, south and west of the furnacesince this tendency causes unbalance of charging and affects thevariation of the wall thickness.

FIG. 3(C) is an example of the oscillogram of the solid borne soundshowing the aggravated condition wherein the inside of the furnace hasbecome so unstable that the burdens do not fall down and, accordingly,there is the possibility of slip within the furnace at any moment. Thisoscillogram shows the occurrernce of a local slip. And when a slip on alarge scale occurs, this phenomenon is observed at all the detectingpoints. And it becomes possible to locate the position of the slip andto foresee it. The condition of the furnace becomes more and moreunstable and finally hanging occurs. It is understood that hangingoccurs because, in general, hard deposits are formed on the innersurface of the furnace to prevent temporarily the burdens from fallingdown. Accordingly, it can be said that the wall thickening phenomenonforetells the possibility of hanging. The sudden change of the solidborne sound level as shown in FIG. 3(C) directly indicates theconsiderable unbalance of the furnace condition. Immediately after theend of this phenomenon, hanging will occur.

Accordingly, as soon as said phenomenon occurs, adequate measures mustbe taken according to the measured values or engineering judgement ofthe furnace condition, such as drop of the inner pressure (for example,in high pressure operation the pressure is dropped from 2.5 atmosphericpressure to 1-l.5 A.P., and in low pressure operation from 1.5 to l-0.5A.P.), reduction of blast and airflow, adjustment of the position oramount of blow-in of hot air and heavy oil, temporary suspension of theblow-in, or change of position or amount of charging by adjusting therotation of the charging bell to a specific angle, etc.

FIG. 3(D) is an example of the oscillogram showing that the wallthickness nearby the detecting points increases suddenly and that thepossibility of occurrence of hanging grows large. This oscillogram showsthat this wall thickness occurs toward south and west. Generally, thisphenomenon tends to occur continuously for several days before theoccurrence of hanging. Therefore, this is an effective source ofinformation in foreseeing the position and the time of the expectedoccurrence of hanging. This figure faithfully depicts the transition ofthe blast furnace condition recovering from the hanging wherein in acouple of or several days from the formation of hanging, the harddeposits fell down and then the normal furnace operation was resumed.

FIG. 3(E) is an example of the oscillogram showing the solid borne soundlevel catching the so-called hanging phenomenon which begins to occurseveral hours before the actual completion of the hanging. The curves ofthe oscillogram show that when the hanging phenomenon begins to occur (Kat the north portion of the furnace, the deposits on the inner surfaceof the furnace suddenly grow, and, as a result of the fact that the gasfiow changes at the section and is suddenly reduced, the solid bornesound level of the hanging portion drops, and in the west area, the gasflow begins to increase suddenly (N and the solid borne sound levelrises. All of these show that there is a hanging at the northeast areaof the furnace. Sharp peaks (K H and N at the right ends of the curvesindicate the sound caused by the fall of the hanging, namely the suddenelimination of the hanging.

This indication is very important also in foreseeing whether a newhanging is being formed in the furnace immediately after the fall of theformer hanging or if the normal condition is completely resumed in thefurnace operation.

From the analysis of these oscillograms, it is understood that it ispossible in the method of the present invention to detect the occurrenceof slip and hanging sooner and provide practical means for stabilizingthe furnace operation better than in the conventional method utilizing,for example, sounding rods.

In FIGS. 4(A) and (B), the values of the solid borne sound levelmeasured continuously for several days at eight points selected atnorth, east, south and west around the furnace at the height of the 3rd4 of the shaft height) and the 4th of the shaft height) decksrespectively are plotted in correspondence to the furnace conditions. Asmarked along the ordinate of the graphs shown at the bottom of FIG. 4(A)and FIG. 4(B), the furnace condition is classified into four categories,namely, good, bad, very bad and hanging which are judged by the readingsof the sounding gages (sounding rods) applied at two positions and areshown in the graph in comparison to the curves measured by the method ofthe present invention, wherein the terms are defined as follows:

"hanging represents a condition wherein the readings of the bothsounding gages applied at the two positions do not change;

very bad" represents a condition wherein the readings of the bothsounding gages at the two positions do not change at all or changesuddenly and the level of the burden drops suddenly also;

"bad" represents a condition wherein one of the readings of the soundinggages is similar to those in very bad above and the other shows smoothfall; and

"good" represents a condition wherein both of the readings of thesounding gages show relatively smooth fall and the level of the burdenalso drops smoothly.

The average level of the solid borne sound measured over a long time isexpressed by a chain line in each diagram. From the comparison betweenthe curves and the average level line, it is understood that, both atthe 3rd and 4th decks, the solid borne sound level changes as much as:15 db before and after the hanging, in other words, the magnitude ofthe solid borne sound changes in the range of more than :5 times of theaverage level.

The average level is low at the north and east sides both at 3rd and 4thdecks. This fact foretells that the furnace wall is thick on these sidesand the possibility of hanging is great in these areas. The hangingbegins to occur at the time t1 and last for about hours. In this case,6-7 hours before the time :1, a sudden change of the solid borne soundlevel is observed in the southwest area which is followed by a slip andit seems that the average level is restored once. In fact, however, thefurnace condition becomes worse. The solid borne sound level drops inthe northeast area at 4th deck which shows that a hanging is formed atthat area. If various countermeasures as described above are takenbefore the formation of the hanging, it would be possible to prevent thehanging.

FIG. 5 shows a block diagram of a continuous detecting apparatus to bemounted on the mantle of a blast furnace for measuring the solid bornesound level of the mantle. As described above, for example, a pluralityof bariumor zirconium titanate pick-ups 1 are firmly fixed on the mantleby means of bolt welding or tap screws at more than 4 positions alongthe circumference of the mantle at the height of about A-% from thebottom of the shaft length of the furnace, in other words, the belly. Ifa bolt of 20 mm. in diameter and 200 mm. in length is used and thepick-up is attached at the lending end of the bolt, the temperature ofthe pick-up can be maintained under 70 C. by the cooling effect and,therefore, no further attention is needed to cooling.

It is preferable that pre-amplifiers 2 be provided as near as possibleto the pick-ups. Outputs of these amplifiers are switched in turn byswitch 3 for switching sequentially the pick-ups disposed at eachmeasuring point, supplied to the main amplifier 4, passed through the5,600 Hz.-1l,200 Hz. high frequency band pass filter 5, amplified by theamplifier 6, rectified by the rectifier 7, and converted into the D.C.output by the D.C. amplifier 8 for driving the servo motor M so as todrive the servo motor M through the switch 3' interlocked with theswitch 3. The servo motor has a three-staged tandem potentiometer forinterlinking so as to keep the output amplitude at zero and formechanically rotating the potentiometer 9-1, 9-2 and 9-3. The circuitwithin the chain line comprising 6, 7, 8 and the servo motors M above isa logarithmic compression circuit according to the servo mechanismsystem.

Output of the potentiometer 9-2 is supplied to the integrator 20 wherethe input of the varying solid borne sound level is integrated by timeand the average value of it is recorded in the recorder 13. Theintegrator 20 used here is a variable integrator capable of setting anyintegrating time ranging from the order of several seconds to that ofseveral minutes.

Output of the logarithmic compression circuit, namely the voltagerepresenting the varying solid borne sound level, is applied to theinputs of the floating pen 31 and the integrator 10. To the setting arm32 of the potentiometer 9-3 is applied a voltage from the setter 17representing the predetermined level of the solid borne sound. In thepotentiometer 9-3, accordingly, the signal expressing the deviationbetween the set value from the setter 17 and the variable value providedby the floating pen 31 moved by the servo motor M is applied to theintegrator 10.

As described above, the negative deviation signal indicates particularlythe aggravating tendency of the furnace condition such as hanging. Onthe other hand, since the positive deviation signal has no directrelation to such aggravating tendency of the furnace condition, the signof the negative deviation signal is reversed in the integrator 10 andamplified by multiplying by such a coefiicient as, for example, 3-5while the positive deviation signal is manipulated so as to be weakenedto facilitate the judgement of the furnace condition.

The adder 11 accepts successively the integrated inputs from themeasuring points (only four points are shown in FIG. 4 but generallymore than 10 points are used in actual operation) switched one by one,sums them up and feeds them to the memory circuit 12 of pulse system.This memory circuit 12 is provided for storing the outputs of the adderl1 enlarging the integration time by the number of the memory elementsdisposed in parallel and is constructed so as to accept new signals oneby one, to shift the signals from left to right by one position at eachacceptance of a new signal and to eliminate the oldest signal one byone. The signals presently stored in the memory circuit 12 are all addedin series by the adder l3, matched against the predetermined value inthe indicator 15. And when the output of a signal exceeds thepredetermined output value, an alarm signal is supplied by the outputterminal 16.

Output of each integrator 10 is applied to each indicator 18 and theabsolute value of the average level of the solid borne sounds isindicated. It is possible that the outputs be indicated by the indicator18 as the absolute value of db, or when it is necessary, as the absolutevalue of the wall thickness. Alternatively, when the output of eachmeasuring point is introduced to an adequate calculating unit, theoutput may be expressed as an information signal from the terminal 14and supplied as an absolute output of the solid borne sound level or acontrol signal.

As described above in detail, by measuring the solid borne sound at aplurality of appropriate points on the mantle of the blast furnace andobserving the values measured continuously for a long time, accurateinformation on various furnace conditions, such as wall thickness, slip,hanging and fall of the hanging, can be obtained successively, and byanalyzing such information future furnace conditions can be foreseen andthe blast furnace can be correctively controlled at relatively low cost.Consequently, the present invention provides the optimum method andapparatus for judging the blast furnace condition by using theinformation explained above as the source of control command for thenormal operation of the furnace.

We claim:

1. A method of judging the condition of a blast furnace which comprises:

(a) sensing the level of solid borne sound at a plurality of points inthe mantle of said blast furnace;

(b) generating signals in response to the sensed levels at therespective points; and

(c) displaying indicia representative of said signals as an indicationof the thickness of the furnace wall at said points.

2. A method as set forth in claim 1, wherein said points are distributedabout the circumference of said mantle at each of a plurality of levels,said levels being located between A and of the shaft height of the blastfurnace.

3. A method as set forth in claim 2, wherein said signals are generatedin response to the level of sound in a frequency band between 5,600 Hz.and 11,200 Hz.

4. A method as set forth in claim 1, wherein an alarm signal isgenerated when the thickness of the furnace wall at one of said points,as indicated by said indicia, differs from a predetermined value.

5. An apparatus for judging the condition of a blast furnace comprising:

(a) sensing means mounted on the mantle of said furmate for sensing thelevel of solid borne sound at a plurality of spaced points of saidmantle;

(b) signal generating means for generating respective signals inresponse to the sound levels at said points; and

8 (c) display means connected to said signal generating means fordisplaying indicia in response to the generated signals.

6. An apparatus as set forth in claim 5, further comprising filter meansinterposed between said signal generating means and said display meansfor limiting display to signals generated in response to sound in aselected frequency hand between 5,600 Hz. and 11,200 Hz.

References Cited UNITED STATES PATENTS 3,078,707 2/1963 Weaver 26625GERALD A. DOST, Primary Examiner U.S. Cl. X.R. 2662$

